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Understanding Optical Brighteners in Paper Production

Explore the role of optical brighteners in paper manufacturing, their properties, impact on print quality, and challenges in measurement. Learn how OBAs affect color perception and how to compensate for their influence. Gain insight into paper classification, brightness measurement, and the EU vs. US paper segmentation. Discover how optical brighteners interact with various inks and affect the final print result.

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Understanding Optical Brighteners in Paper Production

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  1. Paper, the Fifth Color Current Classifications Optical Brighteners By Trish Wales Sappi Fine Paper March 15,2006 April 9, 2006

  2. Coated Supercalendered Newsprint Uncoated First SegmentationU.S. vs. EU • Coated • Supercalendered • Newsprint • Uncoated

  3. U.S. Coated Paper Classification Coated Free Sheet Classification Coated Groundwood Classification

  4. Supercalendered Classification

  5. Quality and Use Offset Utility Opaque Premium Opaque Copy Paper Text and cover Writing Papers Bristols Newsprint Finish Smooth Vellum Embossed Laid Wove Uncoated Paper Classification

  6. Brightness

  7. Brightness Illuminant Ink Film Paper Brightness is measured at one wave length 457 nm

  8. Test Methods

  9. Test Comparison

  10. European Classification • Related to paper manufacturing process • Separated by fiber type • Number of coating layers considered

  11. European Papers Art Std WFC Chemical Pulp UWF HWC Mechanical Pulp MWC Std. LWC Relative Price FCO MFC SC Newsprint Relative Quality

  12. ISO 12647-2 • Five types • Optical characterization • Shade/Gloss

  13. ISO 12647-2 Categories • 1. Gloss Coated, woodfree • 2. Matte Coated, woodfree • 3. Gloss Coated, web • 4. Uncoated, white • 5. Uncoated, slightly yellowish

  14. Paper Types

  15. Fluorescence

  16. Optical Brighteners • Prevalent • Increasing • Measurement nightmare • Visual Matching challenge

  17. What are they? • Chemical additives • Textiles • Paints • Paper

  18. Paper OBA Properties • Absorb light in UV More UV, more absorbed, more emitted • Emit in blue region No UV, no emission • Unstable in light • Paper goes from white to yellow

  19. 100 50 Re-Emission 0 300 350 400 450 500 550 600 650 700 Wavelength in nm -50 Absorption -100 Optical Brighteners

  20. OBA affects Print • See effect in the white spaces • See effect through cyan ink • Effect blocked by magenta and black ink • Yellow ink effect depends on ink transparency • On-line measurements give false reading • Pulsed Xenon • White point compensation

  21. Optical Brighteners

  22. Questions????

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